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<script>

function Human(n,a){
    this.name = n;
    this.age = a;
}
Human.prototype.haha = '哈哈';
var obj3 = new Human('王五',25);

console.log( Human.prototype );// {constructor: Human, haha: '哈哈', __proto__ : Object.prototype}
console.log( obj3 );// Human {name: '王五', age: 25}
console.log( obj3.name );// '王五'
console.log( obj3.hehe );// undefined

// 原型链：
// obj3.hehe -> obj3 -> obj3.__proto__ -> Human.prototype -> Human.prototype.__proto__ -> Object.prototype -> Object.prototype.__proto__ -> null => undefined


</script>
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